Brightening and stabilizing the color of metal salts of naphthene- and ethylhexanic acids and their solutions



United States Patent BRIGHTENING AND STABILIZING THE COLOR 0F METAL SALTS 0F NAPHTHENE- AND 'ETHYLHEXANIC ACIDS AND THEIR SOLU- TIONS Arnold Albers and Ernst V'oss, Frankfurt am Main, Germany, assignors to Farbwerke Hoechst Aktien'ge sell- 's'chaft vormals Meister Lucius & Briining, Frankfurt am Main, Germany, a corporation of Germany No Drawing. Filed Feb. 17, 1958, Ser. No. 715,835 Claims priority, application Germany Feb. 22, 1957 o Claims. (Cl. 106-310) The present invention relates to a process for brightening and stabilizing the color of metal salts of the naphtheneand ethylh'exanic acids and their solutions.

It is known that naphthenic acids and alpha-ethylhexanic acid, their metal salts and their solutions have a tendency to change color, or more especially, they readily turn dark upon heating. This applies especially to naphthenic acid with a low acid number and to the metal salts of this acid. The darkening is partially due to a certain content of suliur in the naphthenic acids, and it has been proposed to eliminate such sulfur, for example by heating the acids in the presence of hydrogen peroxide or another peroxide, although alpha-ethylhexanic acid and naphthenic acids tree from sulfur or having been freed from sulfur are also subject to similar darkening phenomena.

Moreover, it has already been described in the literature to admix metal salts of naphthenic acids with polyamines, arninophenols and other antioxidants, which.

most irequently contain nitrogen, so as to bring about a color-stabilization. These substances are, however, known to oxidize readily and to turn dark; moreover, they are very unstable, especially in the heat. Due to this instability, they are effective only for a relatively short time and they exhibit only an inferior stabilizing eifect, especially at a raised temperature.

Attempts have also been made to obtain brighter colored metal salts of naphthenic acid by distilling off accompanying substances which have a great extinction coeflicient, especially iron naphthena'te. Such purification (distillation) is expensive and although it is true that it brightens the color of the starting material, it cannot prevent the dried substances from darkening, especially when they are subjected to a thermal treatment.

The darkening interferes with those metal salts which normally have a light color and serve :as driers for making light colors, varnishes or lacquers. For example, darkened lead or calcium driers cannot be used as naphthenates or salts of ethylhexanic acid for making especially light colored lacquers. The same applies to other metal salts of the aforesaid acids, ior example, zinc, cerium, lanthanum or zirconium salts, and for example, zirconyl salts or salts of similar metals.

Now, we have found that the darkening of metal salts, for example, the salts of the aforesaid metals and the darkening of solutions of these metal salts must be attributed to a catalyzed decomposition of the respective acids, a phenomenon which can be inhibited by admixing the metal salts with certain additions. In accordance with our invention, the metal salts to be stabilized or their solutions are admixed with tin salts soluble in these solutions. It is especially preferred to use the tin salts of naphthenic acid or alpha-'ethylhexanic acid (octanic acid), but there may also be used the tin salts of other acids, for example, resin acids.

The use of a tin salt of the same acid which also appears in the metal salts to be stabilized involves the advantage that Patented Oct. 25, 1960 (:1) Apart from tin metal, no foreign substances appear in the drier, and that (b) All other properties of the metal salts or their solutions, such as drying effect and clear solubility, are

' aforesaid acids in admixture with one another.

In preparing the drier, it is preferred first to wash the drier 'to completion, then to add the tin salt and subsequently to dehydrate the drier by heating, so as to prevent the risk that the tin salt is washed out and becomes inactive. V

A small amount of tin salt sufiices already to obtain a very light colored drier not liable to substantial darkening even when'it is heated for a prolonged time to l20150 C. It is preferred to use ODS-2.0% by weight of tin metal in the form of the corresponding tin salt and calculated upon the solid drier. An amount outside the range indicated above, for example, 0.01% by weight or, for example, 3% by weight of tin salt may, however, also be used with good success. The salts of bivalent tin proved somewhat more effective than those of te'travalent tin, but the latter may also successfully be used.

A color-stabilizing drier of the type described above can be melted without undergoing darkening. This fact is of special importance for the removal of molten material firom a drum.

Too dark, not color-stabilized driers which have been dissolved in organic solvents can be brightened to some extent by a subsequent addition of tin salts.

It can be observed during several weeks that the drier admixed with a tin salt is increasingly brightened. The brightening finally comes to a standstill and gradually decreases to some extent.

The color-stabilizing eifect of the stabilizers used in this invention is indicated in Tables I to III below. The color indexes indicate in each particular case how many milligrams of iodine must be dissolved in 1 liter of an aqueous potassium iodide solution to bring about the sanie color impression as with the corresponding metal salt.

The color indexes indicated in Table I were obtained by dissolving solid, unstabilized, lead naphthenate in TABLE I Color-stabilization 0 lead naphthenate containing 15.5% by weight 0] lead with the tin salts of alpha-ethylhexanic acid or naphthenic acid, respectively Color index for stabilization with tin salt of alphanaphthenic ethylacid hexanic acid Percent tin metal on lead naphthenate (solid): V,

no addition (blank test) {gg 28 gg by learn; a a New stars; a a iieliii fflii l5 l? 2.0% by weight tin {iglt iii f 5 .11 i? ii 3 white spirit until the metal content was 15.5% by weight; the lead naphthenate was then color-stabilized.

The word heated as used in Table I is intended to mean that the specific specimen was kept for 3 hours at a temperature of 150 C. before the respective color index was determined.

It is obvious from the tables that the tin salts added prevented lead naphthenate from darkening upon heating. The untreated specimens establish that the tin salt exerts a subsequent brightening effect on lead naphthenate. For example, the addition of 2% by weight of tin metal, calculated on the solid lead naphthenate, reduces the color index from 20 to 16.

Table II indicates the color-stabilizing effect of various tin salts in the preparation of solid lead naphthenate (metal content: 31% by weight), of lead naphthenate dissolved in white spirit (metal content: 15.5% by weight), of solid zinc naphthenate (metal content: 12% by weight), and of zinc naphthenate dissolved in white spirit (metal content: 6% by weight).

TABLE II Table III establishes that the tin salt exerts its stabilizing action notwithstanding the process used for making the lead naphthenate to be stabilized.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

We claim:

1. The process for stabilizing the light .color of waterinsoluble metal salts of organic acids which comprises preparing a homogeneous mixture of water-insoluble salts of metals selected from the group consisting of tin, lead, zirconium, cerium, lanthanum, zinc and calcium, said mixture containing as essential ingredients (1) a tin salt of an acid selected from the group consisting of naphthenic acids, resinous acids and a-cthyl hexanic acid and (2) a member selected from the group consisting of salts, of one of the aforesaid metals other than tin, of

naphthenic :acids, of ot-ethyl hexanic acid, and mixtures Color-stabilization of lead naphthenate and zinc naphthenate with various tin salts metal Percent color index content, Sn-metal color after heat- Product percent stabilizer on solif index ing for 3 y product hours at weight 160 0.

unsfahili'mrl 140 180 Lead naphthenate solid 31 bivalent tin salt of alpha-ethylhexanic acid 0.3 35 35 bivalent tin salt of naphthenic acid 0.3 40 40 bivalent tin salt of resinic acid 0. 3 75 75 nrmtahiliwd 15 110 Lead naphthenate dissolved in 15 5 bivalent tin salt of alpha-ethylhexanic acid 0.3 8 13 white spirit. bivalent tin salt of naphthenic acid 0. 3 9 16 bivalent tin salt of resinic acid 0. 3 27 bivalent tin salt of alpha-ethylhexanic acid 0. 15 Lead naphthenate solid 31 and 0.3 40 4O bivalent tin salt of naphthenic acid, mixed. 0. 15 Lead naphthenate dissolved in bivalent tin salt of alpha-ethylhexanlc acid... 0. 15

White spirit. 15. 5 and 0.3 9 16 bivalent tin salt of naphthenic acid, mixed 0.15 Lead naphthenate 31 tetravalent tin salt of naphthenic acid 0.3 65 Lead naphthenate dissolved in 15. 5 do 0.3 10 43 white spirit. unstabllized.. 150 190 Zinc naphthenate solid 12 bivalent tin salt of alpha-ethyl-hexanic acid 0.3 bivalent tin salt of naphthenic acid 0.3 65 -Zinc naphthenate dissolved in unstabili 1nd 19 65 white spirit. 8 bivalent tin salt of alpha-ethyl-hexanic acid-.. 0.3 8 33 bivalent tin salt of naphthenic acid 0. 3 10 36 thereof, the tin salt being present in an amount by weight from about 0.01 to about 3.0%, calculated as metallic tin and referred to the amount of said other salts.

2. A composition comprising a homogeneous mixture of water-insoluble salts of metals selected from the group consisting of tin, lead, zirconium, cerium, lanthanum, zinc and calcium, said mixture containing as essential ingredients (1) a tin salt of an acid selected from the group consisting of naphthenic acids, resinous acids and a-ethyl hexanic acid and (2) a member selected from the group consisting of salts, of one of the aforesaid metals Color-stabilizing efiect of tin salts on lead naphthenate dissolved in white spirit (metal content 15.5% by weight) and prepared by two difierent processes Percent Sn-mctal color Preparation of the lead naphthenate solution stabilizer on solid index lead naphthenate Solid lead naphthenate prepared as usual by double renone- 20 action, dried. Dissolved in white spirit and adjusted to metal content of bivalent tin salt of alpha-ethyl-hexanic acid 0. 25 9 15.5% by weight. Lead naphthenate prepared by double reaction in the none- 13 presence of white spirit. Repeatedly washed with water and dehydrated by distilling oil the water and part of white spirit. AdJQSFtGd to a metal content of 15.5% by weight with white bivalent tin salt of alpha-ethyl-hexanlc acid 0. 25 8 spin 5 other than tin, of uaphthenic acids, of a-ethyl hexaznic acid, and mixtures thereof, the tin salt being present in an amount by Weight firom about 0.01 to about 3.0% calculated at metallic tin and referred to the amount of said other salts.

3. A composition comprising a homogeneous mixture of Water-insoluble salts of metals selected from the group consisting of tin, lead, zirconium, cen'um, lanthanum, zinc and calcium, said mixture containing as essential ingredients 1) a tin salt of "an aoid selected tfmom the group consisting of naphthenic acids, resinous acids and Jr-ethyl hexanic acid and (2) lead naphthenate, the tin salt being present in an amount by Weight from about 0.01 to about 3.0% calculated as metallic tin and referred to the amount of said other salt.

4. The process as claimed in claim 1 wherein said 10 feared to the amount of said other salts.

References Cited in the file of this patent UNITED STATES PATENTS Minlich et a1. Mai. 25, 1941 

1. THE PROCESS FOR STABILIZING THE LIGHT COLOR OF WATERINSOLUBLE METAL SALTS OF ORGANIC ACIDS WHICH COMPRISES PREPARING A HOMOGENEOUS MIXTURE OF WATER-INSOLUBLE SALTS OF METALS SELECTED FROM THE GROUP CONSISTING OF TIN, LEAD, ZIRCONIUM, CERIUM, LANTHANUM, ZINC AND CALCIUM, SAID MIXTURE CONTAINING AS ESSENTIAL INGREDIENTS (1) A TIN SALT OF AN ACID SELECTED FROM THE GROUP CONSISTING OF NAPHTHENIC ACIDS, RESINOUS ACIDS AND A-ETHYL HEXANIC ACID AND (2) A MEMBER SELECTED FROM THE GROUP CONSISTING OF SALTS, OF ONE OF THE AFORESAID METALS OTHER THAN TIN, OF NAPHTHENIX ACIDS, OF A-ETHYL HEXANIC ACID, AND MIXTURES THEREOF, THE TIN SALT BEING PRESENT IN AN AMOUNT BY WEIGHT FROM ABOUT 0.01 TO ABOUT 3.0%, CALCULATED AS METALLIC TIN AND REFERRED TO THE AMOUNT OF SAID OTHER SALTS. 